Abstract

A high refractive index Te-enriched bulk chalcogenide glass Ge20As20Se14Te46 (n≈3.3) has been patterned by ablation using four- and two-beam interference femto-second laser setups operating at 800 nm. The regular arrays of 0.8 μm diameter and more than 0.8 μm depth holes and/or grooves of typical size of 1×1 mm2 have been written on the surface of the glass in a time-scale of 1 second with 50 femtosecond pulses. The high photosensitivity of this narrow-gap semiconductor glass to the femtosecond irradiation is ascribed to a free electron absorption typical of metals, which is caused by laser-induced heating of the glass.

Figures (3)

Scanning electron microscope (SEM) images of the surface relief of the Ge20As20Se14Te46 glass consisting of air holes (a) or air grooves (b) written in 1 second by means of four (a) and two (b) interfering beams of the fs Ti-sapphire laser, as described in Experimental. The dark spots in (a) and wide dark bands in (b) are the depths of the relief. Some ablated and precipitated powder material is seen as bright irregular shapes between the holes in (a) and as bright sparkling points in (b). The laser parameters were: λ,=800 nm, pulse duration 100 fs, repetition rate 50 Hz (i.e. 50 fs pulses in 1 second of this writing), irradiance 100 μJ/pulse/cm2. The interference half-angle equals to 20° for each of the couples of the interfering beams in (a) and for one couple of the interfering beams in (b).

The relief patterns on the surface on the Ge20As20Se14Te46 glass consisting of air grooves (wide dark parallel lines) and glass ribs (bright parallel lines) perforated by air holes (small dark spots). The laser writing parameters are as in Fig.1, but an irradiance of the source Ti:sapphire laser beam was at 150 μ/pulse/cm2.

A magnified image of the grooves (dark wide parallel lines) written on the surface on the Ge20As20Se14Te46 glass by means of two interfering beams; writing conditions as in Fig.1(b). The sparkling bright spots represent the ablated powder precipitated on the surface, as in Fig. 1(b).